$\displaystyle x^2+y^2-2x+4y=-6$

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- Sep 1st 2007, 11:19 AMdeathtolife04How would I complete the square for this equation?
$\displaystyle x^2+y^2-2x+4y=-6$

? - Sep 1st 2007, 11:23 AMJhevon
- Sep 1st 2007, 11:32 AMdeathtolife04
- Sep 1st 2007, 11:41 AMTKHunny
Yes, you have some problems, there. Who told you it was a circle? It's not necessarily invalid, unless it's supposed to be a circle. Where did you get it and what was the original problem statement?

- Sep 1st 2007, 11:45 AMJhevon
you could have written: $\displaystyle (x - 1)^2 + (y + 2)^2 = -1$

this is not a circle (unless you made an error), since we could not have a negative number on the right hand side if it were a circle.

unless maybe the circle has a radius in the complex plane, but i don't think that makes sense, never did complex analysis - Sep 1st 2007, 12:04 PMdeathtolife04
- Sep 1st 2007, 12:05 PMJhevon
- Sep 1st 2007, 12:07 PMdeathtolife04

Here was the original problem statement: CLICK HERE - Sep 1st 2007, 12:08 PMdeathtolife04
- Sep 1st 2007, 12:10 PMKrizalid
Probably will, 'cause it's really counterproductive a circle with a negative radius :eek:

- Sep 1st 2007, 12:11 PMJhevon
well, it's none of those if it's of the form $\displaystyle (x - h)^2 + (y - k)^2 = c$ where $\displaystyle c < 0$

so maybe "none" is an option. i vaguely remember something about "degenerate conics" but i'm not sure if this applies here. could you say "degenerate circle" i don't know and very much doubt it - Sep 1st 2007, 12:13 PMdeathtolife04